For an optical module for high-speed optical communication or the like, an optical modulator that modulates signal light is used. The optical modulator modulates intensity of optical signals outputted according to electric input signals. For example, in Japanese Patent Application Laid-Open Publication No. 2005-252251, an optical modulation device using an EA (Electro-Absorption) optical modulator is described. The optical modulator modulates the intensity of continuous light on the basis of inputted modulation signals. The modulation signals reach 10-40 GHz or higher. Therefore, for transmission of the modulation signals, design in consideration of high frequency transmission is carried out.